Long-term effectiveness and socioeconomic impact of Eco-DRR measures in Nepal: lessons from JICA's projects

The technique, which combines bioengineering with civil engineering structures such as gabion check dams and gabion walls for erosion and slope protection, has been acknowledged as an example of ecosystem-based disaster risk reduction (Eco-DRR), playing a key role in nature-based solutions (NbS) for disaster risk management and environmental sustainability. However, the extent to which these measures maintain their functionality remain only partially understood. Additionally, it is necessary to assess their socioeconomic impact to understand how these measures affect local communities and livelihoods. This study examines three sites in Nepal—Pipaltar (Upper), Dahachowk, and Nallu Khola— where JICA’s aforementioned techniques were implemented between 1991 and 2007 to address gully erosion, debris flow, and landslides. We assess their long-term effectiveness and impact decades later through field surveys, temporal photo comparisons, and interviews with local residents. Photo comparisons of the Pipaltar (Upper) and Dahachowk sites show an increase in vegetation cover, including bamboo and forests, in areas that were previously degraded, indicating that the measures are functioning effectively. Furthermore, while the gabion check dams for gully erosion control at the Pipaltar (Upper) site showed some deformation over time due to corrosion and breakage of the steel wire, we observed sediment being trapped by the check dams and vegetation establishing in the sediment deposition areas just behind them. This suggests that the gullies are stabilizing and the areas are becoming suitable for vegetation growth. In addition, the debris flow induced by the rainfall event from September 26-28, 2024, in Nallu Khola was somewhat regulated in the creeks where gabion check dams and channel works had been applied. However, in some areas, these structures were buried or destroyed. The socioeconomic impact assessment of the Pipaltar (Upper) site showed that in the past, residents relied on vegetation (e.g. bamboo) planted for gully erosion control, using it for purposes such as making fencing, grass brooms, and livestock feed. However, this is no longer the case, as economic development has shifted their primary source of livelihood to the harvest from their private lands.